/*
 *  Copyright (C) 2010 Matthias Buch-Kromann <mbk.isv@cbs.dk>
 * 
 *  This file is part of the MatrixParser package.
 *  
 *  The MatrixParser program is free software: you can redistribute it and/or modify
 *  it under the terms of the GNU Lesser General Public License as published by
 *  the Free Software Foundation, either version 3 of the License, or
 *  (at your option) any later version.
 * 
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU Lesser General Public License for more details.
 * 
 *  You should have received a copy of the GNU Lesser General Public License
 *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

package org.osdtsystem.matrixparser.learners;

import org.osdtsystem.matrixparser.features.WeightVector;
import org.osdtsystem.matrixparser.features.FeatureVector;

/**
 * A logistic scoring function. The function transforms the linear score
 * in the interval ]-infinity,infinity[ to the "probability" interval ]0,1[
 * by applying the logistic function to the linear score.
 * @author Matthias Buch-Kromann <mbk.isv@cbs.dk>
 */
public class LogisticScorer implements Scorer {
    public double getScore(WeightVector weights, FeatureVector fv) {
        return(1 / (1 + Math.exp(-fv.innerProduct(weights))));
    }
}